Suspension Upgrade?

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Re: Suspension Upgrade?

Postby bikerector » May 17th, 2013, 5:04 pm

300hp wrote:
Generally, on a bike like yours, you should set sag for weight, and tune compression for rider ability. With the shock full open (rebound all the way out, CTD in "D") set sag to 15-20% of the length of the stanchion.

If your bike still blows thru the travel, and you have a high volume air shock, consider this very cheap, highly effective mod (you can do the same thing for free if you have a high volume shock by shimming the high volume can....search MTBR for that). http://www.pinkbike.com/news/tech-tuesd ... -2011.html


This is perfect, I had asked fox if they could tune the shock for me after having to send it in for warranty (ball detent for CTD selector was a PITA to turn and eventually came out) and they said there was nothing they could do to tune it. I think I specifically mentioned revalving it or something since that's how i thought damping would be altered, besides changing oil weights and volumes, like suspension forks. I assume that can be done with mtb forks, I know it can be done with motorcycle forks. Since I'm heavy, 220, it seems like I might be a good candidate for some volume reduction, albeit maybe just a little. Seems like fox has gone out of their way to make their newer air shocks and forks more linear with CTD, according to pink bike. If nothing else, would be worth a try just to see.

I set the sag per fox's instruction the day I got the bike. I'm pretty happy with the sag setting in that I think it's where it should be. My last outing I used probably 80% of the travel and I wasn't being aggressive in regards to hopping off of stuff, was there more for the workout and to get used to the new race tires. The trail is bumpy but there's not much for drops on most of the trail, you have to make the drops bigger by jumping a little and going into them faster.

I have some things to start messing with anyway. I have all of my various settings trials written down since I've had the bike in March and notes next to them, good to go back to if I'm off the bike for a few weeks when I'm getting ready for other types of racing. I know what too much and too little psi is so I have a range to work within anyway.

:icon_thumright: Thanks guys. Weekend is here and the weather is going to be good.
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Re: Suspension Upgrade?

Postby 300hp » May 17th, 2013, 10:28 pm

Try this in the mean time

http://forums.mtbr.com/turner/dw-5-spot ... 03070.html

I actually prefer it as a method to tune if you have this style air can. The less you remove the main can seals, the better.

Don't be afraid to put a fair amount of material in there. When I was bracketing suspension settings, I filled the can, then backed off from there. In your case, I would start by filling roughly 15% of the HV can and set sag to where you have been, and go from there.

Finally, if you want a shock that will stay up in its travel, try a monarch, or a new manitou radium RL. Both have much better dampening for aggressive riding, and are end-user serviceable.

Good luck!

H
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Re: Suspension Upgrade?

Postby bikerector » May 18th, 2013, 5:53 am

Not against getting a new shock but with these different mods available it seems like i should be able to get the air shock tuned ti have the lower volume required to have a much more progressive springrate.

Just so I'm clear, is the outer piece that is off in the mtbr.com link the outer shell/can? Having had mine apart at one point it seems like it has the outer can, shaft and all the internals inside or hidden in or under the shaft.

And if I'm not mistaken, the home made shims are simply replacements for the shims you would have to buy from, as in they are applied in a similar manner?
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Re: Suspension Upgrade?

Postby c0nsumer » May 18th, 2013, 7:16 am

Fox sells a volume reduction kit. See here. At that price (~$25 for the set) I don't think it's worth trying to make them yourself.
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Re: Suspension Upgrade?

Postby bikerector » May 18th, 2013, 7:56 am

c0nsumer wrote:Fox sells a volume reduction kit. See here. At that price (~$25 for the set) I don't think it's worth trying to make them yourself.


I saw that but they say they are compatible with float RP series shocks, in general. I have an inquiry out to see if they will work with the float CTD shocks. Nothing suggests they wouldn't work they just don't say that they will, from what I've seen.
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Re: Suspension Upgrade?

Postby 300hp » May 18th, 2013, 9:48 am

The CTD shock is an rp shock. It is nothing different, except the "p" settings are not called "t" settings. 100% marketing.

Consumer: The volume reduction kit is a great product, and if you have a slim (read, low) volume air cannister, it is the only option for volume reduction.

If you have one of these with the outer sleeve over the regular can
Image

The home made shims are a viable option, and I prefer them because of how easy it is to adjust shim volume to your needs. While I'm making it sound very homebrew, note that Rockshox sells a monarch air can tuning kit, which are simple rubber bands that go between the main air can and the sleeve in the manner discussed above.
Image

Ultimately, I would go the fox route, but I don't see any reason why a little test n tune can't happen this weekend :)

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Re: Suspension Upgrade?

Postby bikerector » May 18th, 2013, 11:02 am

Probably going to have to go with the fox kit since I don't have an outer sleeve. Pretty sure when I pulled it apart last time when trying to figure out what happened to the selector it was just the can and main shaft. Also knowing how simply that area is, just an air reservoir, seems like just putting something in there that would take up space and not jiggle around would be a reasonable option, if the fox solution wasn't an option or it doesn't work.

Is adding oil to a rear shock a viable option for taking up volume? Seems a common solution for forks.
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Re: Suspension Upgrade?

Postby 300hp » May 18th, 2013, 2:13 pm

oil: kind of, not really. For an interim solution it will work but eventually get pushed out.

Now, you can put some slick honey up in the top of the shock behind the bottom out bumper and metal washer, that will stay put pretty darn well and reduce volume.

For short term though, oil works just fine. You can pull the schrader core after you let the air out, squirt 5-7cc of fork oil in there with a baby medicine syringe, and go from there.
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Re: Suspension Upgrade?

Postby c0nsumer » May 18th, 2013, 2:15 pm

If I may suggest, if your shock hasn't had the seals replaced in a while (or ever), do them when you add the Fox kit. It's a super-easy procedure and will add very little time to the overall project.
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Re: Suspension Upgrade?

Postby 300hp » May 18th, 2013, 2:35 pm

Agreed. Treefort has the seal kit for the excellent price of $14 right now.
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Re: Suspension Upgrade?

Postby bikerector » May 18th, 2013, 7:37 pm

The bike was new this spring, doesn't seem like I should need new seals but will get them if it's still recommended. Might be good to add them to get free shipping (LBS can't get fox shock stuff through their distributors).

Had the bike out at Bass River, not exactly a place to kill the suspension but that where the couple of us were riding at. Made a few changes to air pressure before hand to see how much higher I could go, the answer was not much or I would be around 10% sag. Went back to the settings I've been working on all week and they felt really good during the ride, but again, nothing resembling a big hit, people frequently ride cyclocross bikes on the course. Did feel controlled over a few log piles though which was nice.

The real testing came afterwards when I was just noodling around the area and noticed a car going down the long entry drive to the lake in the middle of the area and noticed it was about bottoming out from the pot holes in the gravel drive. Figured why not, so I took off hitting every pot hole I could for about a mile of the gravel road, many were a good 1-2 feet deep and many in a row. The good news was that I didn't blow through all the travel, so I must have gotten something right while tinkering. I think I had about 20% left in the rear, not as much in the front but that's because at some point I turned the knob to descend mode to see what it would do, doesn't feel like much but it used more travel so it must have done a little.

Okay, so the biggest thing I learned from the gravel stuff was what the rebound damper does. A question, the knob has clicks, but do you have to adjust to the click or are they more for reference? With the knob where I had going to the trail, some of the time the fork would come off the ground from the force of the rebound combined with the upward motion of the "out" side of the pot hole is this about where you want it? if I went one full click harder, about one full turn I think, it seemed like the fork never fully extended before hitting the next hole, and the difference was very obvious. Should my setting be somewhere between the clicks or is one of those seem like where it should be?

Back to the air pressure and volume change thing, my under standing is that I would want the more progressive rate, take out volume/add insert, for being able to take bigger shocks, but it would have little affect at the top of the travel, small bump compliance, because it more progressive nature of the shock affects the end of the travel more than the top of the travel. Do I have this figured out? I feel like I have the small (roots and such) to mid bump (pot holes/ steps) stuff figured out, so probably 90+% of XC riding, it's just the harder hits or "oops I took that log pile wrong" that needs the tinkering still.

Might be going to Copper Harbor next month for a week so it would be sweet to have this figured out in case I can get the time off work to go. I've never been there but it seems like this bike should be good for it. Hope so, everyone else in the group is on hardtails.

Again, thanks everyone for the help. It greatly helps to know what's going on underneath me to put "sensation" to "what the suspension is doing."
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Re: Suspension Upgrade?

Postby meangreen » May 20th, 2013, 3:18 pm

Regarding the rebound damping: Take a few harsh bumps mid-corner at speed, and the answer will be pretty clear:) Less rebound damping will help mid corner stability (keeping you on-line), but will also 'feel' softer and less responsive IME.
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Re: Suspension Upgrade?

Postby 300hp » May 20th, 2013, 9:29 pm

The classic test for getting your rebound in range is to slowly roll off a curb seated, no brakes. the rear shock should compress, rise, and settle. If it oscillates a couple times, it's probably too fast. If it barely rises and doesn't settle, it's too slow. For perspective, allow yourself to bracket settings, roll of the same curb at the same speed with full open rebound, then with full closed rebound, then do it at the middle click of the range.
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